1. Field of the Invention
The present invention relates to a soft focus lens barrel.
2. Description of the Related Art
In a known soft focus lens barrel, a soft focus can be controlled by varying the magnitude of spherical aberration. However, professional photographers or highly skilled amateur photographers sometimes want to emphasize a deformation caused by a curvature of field.
The present invention provides a soft focus lens barrel in which not only spherical aberration but also a curvature of field can be controlled by a simple structure.
According to an aspect of the present invention, a soft focus lens barrel is provided, including a stationary barrel to be secured to a camera body; first, second, third and fourth lens group frames which hold a first lens group, a second lens group, a third lens group and a fourth lens group, respectively, the first through fourth lens group frames being supported by the stationary barrel so as to move in an optical axis direction; a distance operation ring, a soft focus operation ring, and an image surface operation ring, each being supported by the stationary barrel so as to independently rotate; a focus guide mechanism which varies a resultant focal position of the first through fourth lens groups by moving the first and second lens group frames in the optical axis direction without varying the distance between the first and second lens group frames in accordance with a rotation of the distance operation ring; a spherical aberration guide mechanism which varies spherical aberrations produced by the first through fourth lens groups by moving the third and fourth lens group frames in the optical axis direction along predetermined paths, in accordance with a rotation of the soft focus operation ring; and a field curvature guide mechanism which varies a curvature of field produced by the first through fourth lens groups by solely moving the first lens group frame in the optical axis direction, in accordance with a rotation of the image surface operation ring.
It is desirable for the second, third and fourth lens group frames to be supported so as to move linearly in the optical axis direction but not to rotate about the optical axis, the first lens group frame being supported so as to rotate and axially move relative to the second lens group frame.
It is desirable for the first lens group frame and the image surface operation ring to be connected to each other so as to move relative to each other in the optical axis direction and rotate together, and wherein a cam mechanism is provided between the first lens group frame and the second lens group frame to relatively move the first and second lens group frames in the optical axis direction when a relative rotation occurs between the first and second lens group frames.
It is desirable for the distance operation ring and the second lens group frame to be associated with each other so that the second lens group frame is moved linearly in the optical axis direction in accordance with a rotation of the distance operation ring, the first lens group frame being engaged with the second lens group frame so that the first lens group frame is moved together with the second lens group frame in the optical axis direction when the image surface operation ring is not rotated.
According to another aspect of the present invention, a soft focus lens barrel is provided, including a stationary barrel secured to a camera body; first, second, third and fourth lens group frames which hold a first lens group, a second lens group, a third lens group and a fourth lens group, respectively, the first through fourth lens group frames being supported by the stationary barrel so as to move in an optical axis direction; a distance operation ring, a soft focus operation ring, and an image surface operation ring, each being supported by the stationary barrel so as to independently rotate; a focus guide mechanism which varies a resultant focal position of the first through fourth lens groups by moving the first and second lens group frames in the optical axis direction without varying the distance between the first and second lens group frames in accordance with a rotation of the distance operation ring; a spherical aberration guide mechanism which varies spherical aberrations produced by the first through fourth lens groups by moving the third and fourth lens group frames in the optical axis direction along predetermined paths, in accordance with a rotation of the soft focus operation ring; and a field curvature guide mechanism which varies a curvature of field produced by the first through fourth lens groups by moving the first lens group frame and the second lens group frame at predetermined paths in the optical axis direction, in accordance with a rotation of the image surface operation ring.
It is desirable for the focus guide mechanism to be provided with a focusing movement frame which is moved linearly in the optical axis direction in accordance with a rotation of the distance operation ring, the first lens group frame being supported so as to move relative to the focusing movement frame, the second lens group frame being supported by the first lens group frame so as to move only linearly in the optical axis direction, so that when no relative rotation of the first lens group frame to the focusing movement frame takes place, the first and second lens group frames are moved in the optical axis direction together with the focusing movement frame.
It is desirable for the first lens group frame and the image surface operation ring to be connected to each other so as to move relative to each other in the optical axis direction and rotate together, wherein a first cam mechanism is provided between the first lens group frame and the focusing movement frame to relatively move the frames in the optical axis direction when a relative rotation occurs between the first lens group frame and the focusing movement frame, and wherein a second cam mechanism is provided between the second lens group frame and the focusing movement frame to relatively move the frames in the optical axis direction when a relative rotation occurs between the second lens group frame and the focusing movement frame.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2002-208508 (filed on Jul. 17, 2002) which is expressly incorporated herein by reference in its entirety.